Optical Fiber-Tip Heat Sensor Featuring a Multipositional Fabry–Pérot Cavity Resonator

A Fabry-Pérot cavity (FPC) resonator featuring a multi-positional, hinged mirror monolithically fabricated by two-photon polymerization (2PP) is demonstrated as a temperature sensor. The hinged mirror enables both a concave optical surface and a gold, high-reflective (HR) coating to be integrated into a cavity less than 30 μm long. These features are known to improve the performance of the FPC resonator but could not be jointly realized with previous designs. The resonant wavelength of the device shifts in response to temperature changes, and a sensitivity of 0.191±0.007 /°C over approximately 22.2 - 50.6 °C is demonstrated. This represents only one application of the multi-positional mirror, which facilitates post-processing with directional deposition techniques.